From the second trimester, the gynecologist or midwife measures uterine height at each consultation with a simple tape measure. This gesture may seem rudimentary at the time of ultrasounds, but it gives a good indication of the growth of the baby.

Fundal height refers to the distance between the upper edge of the pubic symphysis (the pubic bone) and the fundus (the highest part of the uterus). It is in a way the size of the belly of the mother-to-be on her height.

From the 4th month of pregnancy until term, uterine height is measured at each prenatal visit (HAS recommendations) (1). The future mother is lying on her back, empty bladder, arms at her sides. After having palpated her belly in order to locate the uterine fundus, the practitioner measures the height of the belly with a simple seamstress meter, the end of which is kept in contact with the upper edge of the pubic symphysis, and the entire length in contact with the skin. , to the uterine fundus.

As the uterus grows in proportion to the baby, measurement of fundal height gives a good indication of fetal growth between ultrasounds of 22 WA and 32 WA, and after examination of 32 WA. The measurement of uterine height and its progression is, as such, one of the screening tools for intrauterine growth retardation (IUGR).

The uterine palpation performed during the measurement also makes it possible to assess the tone of the uterus and to estimate the amount of amniotic fluid. The clinical examination, the stature of the mother, the obstetric history of a baby of low weight or, on the contrary, of a “big” baby are also taken into account to interpret the uterine height.

According to Fournié’s rule, the reference curve mainly used in France, between the 4th and the 7th month of pregnancy (i.e. between 18 and 32 weeks), the uterine height must be equal to or greater than the number of weeks of amenorrhea completed minus 4 (2). At this stage of pregnancy the uterine height increases by 1 cm per week. After 32 weeks and until term, progression slows down and the uterine height increases by 0,5 cm per week. We therefore obtain the following values:

• 4th month of pregnancy: 16 cm;
• 5th month of pregnancy: 20 cm;
• 6th month of pregnancy: 24 cm;
• 7th month of pregnancy: 28 cm;
• 8th month of pregnancy: 30 cm;
• 9th month of pregnancy: 32 to 34 cm.

The position of the baby can indeed affect the uterine height. If it is positioned high in the belly, the fundal height may be a little higher than normal. Conversely, if it is low or in a transverse position (that is to say horizontally), the uterine height may be a little below the average. With the uterine palpation, the practitioner can detect these situations and interpret the measurement of the uterine height accordingly.

The size of the mother-to-be can also influence the measurement of the fundal height. If you are overweight, the presence of fatty tissue in the abdomen can make it a little more difficult to measure fundal height. A study (3) has also reported a difference of 2 cm between measurements of uterine height in thin pregnant women and those suffering from obesity. The practitioner will therefore take these different elements into account.

Insufficient fundal height suggests a “small” baby or oligoamnios (lack of amniotic fluid). An assessment of IUGR, combining an ultrasound and, possibly a blood test (to detect a possible infection which could have had an impact on fetal growth) will be carried out to monitor the growth of the baby and assess the amount of amniotic fluid.

A higher uterine height than normal suggests on the contrary a fetal macrosomia, that is to say a baby of significant weight, or a hydramnios (excess amniotic fluid). Likewise, an ultrasound will be performed to monitor the baby’s growth and assess the amount of amniotic fluid. At the same time, a blood test called OGTT (oral hyperglycemia) will be prescribed to detect possible gestational diabetes, the main cause of fetal macrosomia.